Melissa McCarthy has joked about how she had to undergo tough training to film a food poisoning scene in Bridesmaids.

The cringe-worthy scene in the laugh-out-loud comedy sees Melissa's character Megan and the other bridesmaids - Kristen Wiig, Rose Byrne, Ellie Kemper and Wendi McLendon-Covey - suffer from a painful bout of food poisoning.

"I spent two years in acting school, just rehearsing that - sinkwork - and it finally paid off," she quipped.

She added: "My parents could feel good about paying for that tuition. This is like a horror scene in the movie, it's like watching people try to stop the train that is coming full throttle at them. I love watching people go, 'No, no, no' because it's so embarrassing.

"Everybody has been in some horrific state like that. I think why it works is that Paul (Feig, director) wanted to play it really, really real."

Melissa - who has appeared in film like Life As We Know It and The Back-Up Plan - describes Bridesmaids, co-written by Kristen, as an honest comedy.

"To me, funny is funny. I always watch other female movies and think, 'Who are these women? I don't relate to this'. I just want a funny movie," she said.

"I read this, it's a well-written script. There's parts that are really touching, and it's complicated and messy and to be that funny on top of a really good story, I think everyone appreciates that."